Which factor is essential for the process of natural selection?

Variations in traits are essential for the process of natural selection because natural selection relies on differences among individuals within a population. These differences can affect how individuals survive and reproduce in their environment. For natural selection to occur, some variations must confer advantages that increase an individual's likelihood of surviving to reproduce, thus passing those favorable traits to the next generation.

When traits are varied, it provides a selection pressure for certain traits to become more common in a population over time. If there were no variations, all individuals would be essentially identical, and there would be no differential survival or reproductive success based on traits. This diversity is critical for adaptation and evolution, allowing populations to adjust and thrive in changing environments.